The invention relates to a special construction of a folding machine for the production of foldable containers from a blank transported along a conveyor path with predetermined conveying speed, whose middle part has laterally arranged hinge-like folding grooves with thereto adjoining side flaps, which along their conveying path are first raised from their flattened position by means of turning devices, increasingly tilted inwardly along the folding grooves towards the longitudinal median of the blank, and finally folded together from above and connected to each other.
Such devices, which are special folding machines, are known (see e.g. the brochure "In-Line Machine 2000", Klett Wellpappenmaschinen, Remscheid Germany).
Throughout the present application the terms "device for processing a blank transported along a conveyor path at a predetermined conveying speed" and "folding machine" are used as synonyms, since all features on which the invention is based apply to such a device, as well as to this type of folding machine.
Although the present invention generally relates to a folding machine for the production of foldable containers of a flat material blanks, a preferred embodiment of the present invention is a folding machine for the production of foldable boxes made of foldable cardboard. Particularly corrugated cardboard is used as a starting material.
However we do not intend to limit the invention to blanks of corrugated cardboard. Therefore corrugated cardboard and foldable cardboard are used when no special indication is given. A foldable cardboard comprises also the general concept of foldable container, as long as the foldable container is produced in a folding machine as described by the invention.
Such foldable cardboard blanks consist for instance of corrugated cardboard. For this purpose for each foldable box a corrugated cardboard sheet is provided with a groove parallel to the undulation, hinge-like side flaps adjoin the middle part.
The present invention is not limited to folding machines for the production of foldable containers closed on all sides. It relates also to folding machines for the production of shell-like folding containers. This are for instance protective casings without a top and/or bottom. The problem with such protective casings is that the surrounded object has to fit as accurately as possible within the casing. By eliminating the bottom and/or the top the danger of unintended slide-out of the object exists.
In practice a relevant case occurs e.g. with the casing of headlights for motor vehicles. This headlights are usually fitted in corrugated cardboard jackets. The inner dimensions of the jacket are so tight that the headlight is firmly held.
A further example of use is, as mentioned, a foldable cardboard blanks which corresponds to an unfolded parallelepipedic box with bottom and top.
Such boxes are normally processed on automatic packaging machines. For this reason the quality of the product leaving the folding machine is particularly relevant.
A foldable cardboard blank can be provided with the required slots or notches. For this purpose the corrugated cardboard sheet is slitted, or notched parallel to the undulations in the region of the folding grooves. The slot width equals e.g. 1 cm. The slot depth corresponds to the folding length of the bottom or top. In this way the bottom and top of the foldable cardboard are attached so as to be freely movable relative to the rest of the cardboard. Normally three slots can be precisely cut. A fourth slot is formed in the area of the two folded side flaps meant to be connected to each other. One of the two side flaps is additionally provided with a so-called adhesion border or glue border. This is a tongue which is also provided with a folding groove.
The folding grooves can form a hinge between the side flaps and the middle part. Normally for parallelepipedic boxes four folding grooves are provided. On each side of the middle section one folding groove is provided in addition to one folding groove within the middle part and one folding groove in the area where the two side flaps are brought together.
In such folding machines the optionally prestamped blanks are transported while at the same time the still flattened side flaps of the blanks with the already prepared folding grooves are seized and are tilted inwards during their ride along the conveyor path.
The folding takes place by means of so-called turning belts known per se, which at first seize the side flaps from underneath. The turning belts run from a level below the middle section to a level above the middle section. The axes of the turning belts are so arranged with respect to each other, that the belt surface turned towards the foldable cardboard blank turns by a total of 180 degrees along the conveying path. Therefore normally on both sides of the middle part two such turning belts are arranged in succession, each of the turning belts being staggered by only 90 degrees.